Rates of overweight and obesity are increasing, particularly among individuals aged 18 to 29. An estimated 25- 35 percent of American college and university students are overweight or obese. Contingency Management (CM) is a behavioral intervention that provides tangible rewards for positive behaviors. CM has substantial evidence of efficacy in reducing smoking and drug use and increasing treatment retention and medication compliance. The current study will evaluate the efficacy of a 24-week CM intervention to promote weight loss in overweight and obese university students. Seventy participants with a body mass index (BMI) of 27.0-34.9 will be randomly assigned to one of two conditions: (a) LEARN, a manual guided behavioral weight loss program (Brownell, 2004), with weigh-ins and supportive counseling, or (b) LEARN with weigh-ins and supportive counseling plus CM. Participants in the CM condition will earn chances to win prizes ranging in value from $1 to $100 each week in which they lose at least one pound. Once they lose 5 percent of baseline body weight, they will earn chances to win prizes for weight loss or weight maintenance. Additional chances can be earned by completing activities that promote weight loss. The primary outcomes will be absolute and proportional weight loss from pre- to post-treatment, as well as proportion of participants achieving clinically significant weight loss (>5 percent of baseline weight) and proportion moving into a lower risk BMI category. Secondary outcomes will include length of retention in the study, increase in physical activity level, and improvement in nutritional quality of diet. Effects of the CM intervention on psychiatric distress and self-efficacy and motivation to engage in activities that promote weight loss will also be assessed. We predict that participants in the CM condition will lose more weight than participants assigned to the LEARN program without CM, and that more CM participants will achieve clinically significant weight loss. We also predict that participants in the CM condition will remain in the program longer, show larger increases in physical activity, show greater improvements in diet quality, and have greater increases in levels of self-efficacy and motivation than comparison group participants. Mediators and moderators of CM outcomes will also be evaluated. If efficacious in promoting weight loss in a college population, CM could help to prevent or delay later development of obesity-related medical problems. PUBLIC HEALTH RELEVANCE: Obesity is a serious and prevalent problem with physical, emotional, social, and financial consequences for individuals and the community, and rates of obesity are increasing among young adults. Evidence suggests that students gain modest but significant amounts of weight during the college years. If contingency management is effective in promoting weight loss and healthy lifestyle changes that contribute to weight loss during this high risk period, it could help to prevent the negative consequences of obesity and set the stage for better health outcomes throughout the adult lifespan.